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  • 1
    Electronic Resource
    Electronic Resource
    Enhanced Reactor Performance with Pressure and Vacuum Swing Reaction (2004)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of chemical reactor engineering 2.2004, 1, A19 
    Details
    ISSN: 1542-6580
    Source: Berkeley Electronic Press Academic Journals
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Product separation and regeneration of sorbent was accomplished in a novel pressure swing reactor through pressurisation, adsorption, blowdown and purge steps. The switching from sorption to reaction to regeneration was tested in a two bed sorption/reaction apparatus. Models developed for the mass and momentum transfer in the catalyst bed and sorber, were solved using orthogonal collocation within the method of lines. The effects of operating conditions and cycle configurations on performance were assessed. The results from dynamic experiments with propene metathesis to produce ethene and 2-butene in a fixed-bed catalytic reactor were in agreement with model predictions. Both pressure and vacuum swing demonstrated that conversion and product quality can be enhanced by periodic cycling with greater separation obtained with vacuum swing. The separation of products help reduce the downstream processing costs of exit mixtures, enable reactant utilisation by recycling and improve product handling at subsequent stages. The efficacy of the periodic separating reactor in terms of conversion, product purity and recovery were investigated.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/ijcre/vol2/A19
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  • 2
    Electronic Resource
    Electronic Resource
    Catalyst-Adsorbent Configurations in Enhancing Adsorptive Reactor Performance (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of chemical reactor engineering 5.2007, 1, A108 
    Details
    ISSN: 1542-6580
    Source: Berkeley Electronic Press Academic Journals
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fixed-bed columns containing solid catalysts and adsorbents were employed for simultaneous reaction and separation. The models developed for propene metathesis were validated with experimental data for configurations with and without the effect of pressure swing reaction. The models for the mass and momentum transfer in the catalyst bed and adsorber were solved using orthogonal collocation within the method of lines. The reactor/separator performances were tested for beds with varying numbers of layers of catalysts and adsorbents which were arranged sequentially. The pressure reaction columns behaved as reactor/separators in series. As the number of layers increased, a homogeneous distribution of the catalyst and adsorbent was approached in the limit. These configurations with variable catalyst/adsorbent distributions were investigated for propene metathesis reaction, in terms of product purity, selectivity, conversion, recovery, yield and productivity. Improved reactor performance was observed with a pressure swing separation system and in particular with close to well-mixed reactor/separator configurations.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/ijcre/vol5/A108
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  • 3
    Electronic Resource
    Electronic Resource
    Reactor Operating Strategy and Secondary Nucleation in Emulsion Polymerization (2004)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of chemical reactor engineering 2.2004, 1, A2 
    Details
    ISSN: 1542-6580
    Source: Berkeley Electronic Press Academic Journals
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Particle formation is a key step in emulsion polymerization reactions and has been the subject of extensive investigations in the past few decades. The main aim of this work was to investigate, both theoretically and experimentally, the conditions for secondary nucleation and particle evolution in batch and semi-batch emulsion polymerization. The effects of variation in monomer and emulsifier concentration in the feed, the distribution between the charge and the feed, temperature and the emulsion feed rate on polystyrene particle size distribution were investigated both theoretically and experimentally. The population balance and kinetic models developed were employed for predicting the product attributes for a range of reactor operating conditions. The sets of nonlinear algebraic and integro-differential evolution equations were solved efficiently for this work.Monomer and surfactant feed rates were found to have significant effects on the growth of polymer particles and consequently on the particle size. Different particle sizes and distributions were obtained using the same procedure with variable operating mode. A semi-batch reactor with variable monomer emulsion feed can produce latexes with variable polydispersity. A high initial rate of particle formation could lead to reduction in secondary nucleation and hence to the formation of a mono-modal PSD. This can be achieved by using high initiator and emulsifier concentrations in the feed, a high temperature, or a low monomer concentration in the charge. A low initial rate of nucleation increases the possibility of secondary nucleation and the formation of a bimodal PSD. The evolution of a bimodal PSD requires secondary nucleation after primary nucleation occurs.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/ijcre/vol2/A2
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  • 4
    Electronic Resource
    Electronic Resource
    Calorimetry for Inferential Conversion Monitoring in Emulsion Copolymerization Reactors (2006)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of chemical reactor engineering 4.2006, 1, A7 
    Details
    ISSN: 1542-6580
    Source: Berkeley Electronic Press Academic Journals
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic model was developed describing emulsion copolymerization of styrene and MMA within a batch/semibatch stirred tank reactor. This model includes the initiation, propagation, transfer and termination steps of the monomers styrene and MMA. It also includes the mass and energy balance equations for the polymeric radicals. Energy balance equations incorporate the heat of reaction, internal and external heat transfer effects, as well as heat losses. The resulting sets of (differential/algebraic) equations were solved for both species concentrations and temperature profiles as functions of time. Experiments were conducted in a laboratory reactor, instrumented with platinum resistance thermal transducers and gravimetric conversion measurement devices. Thermal measurements in conjunction with the energy equations helped estimate monomer conversions as a function of time. The kinetic model predictions of conversion compared well with inferential calorimetric measurements, which were validated using gravimetric data. The experiments were run at variable operational conditions in terms of feed rate, temperature and monomers feed ratio. The calorimetric model was used as a soft sensor for the prediction of the rate of reaction, conversion and molar mass.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/ijcre/vol4/A7
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  • 5
    Electronic Resource
    Electronic Resource
    Periodic and nonperiodic dynamic responses for sorption diffusion and reaction in a Berty reactor (1994)
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 33 (1994), S. 102-108 
    Details
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ie00025a014
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  • 6
    Electronic Resource
    Electronic Resource
    Comments on "Moisture desorption in cellulosic materials" (1993)
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 32 (1993), S. 1800-1800 
    Details
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ie00020a040
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  • 7
    Electronic Resource
    Electronic Resource
    Selenium Associations in Estuarine Sediments: Redox Effects (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 275-282 
    Details
    ISSN: 1573-2932
    Keywords: selenium ; sediment ; estuaries ; sequential extraction ; redox potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Selenium (Se) is a contaminant of concern in environments affected by discharges from smelting and coal-burning industries. Experiments have been performed to investigate the phase associations of selenium in contaminated sediments under a range of controlled redox conditions. In this study, Se sediment associations were examined using the BCR sequential extraction technique after stabilisation at different redox states. It was shown that although most of the sediment-bound Se is associated with the operationally-defined "organic/sulfide" fraction, as the measured redox potential of the system is increased, more Se moves into the "exchangeable" and "iron/manganese oxyhydroxide" fractions. In these fractions, contaminants can be expected to be more bioavailable. As the mass of Se absorbed to sediments is typically at least an order of magnitude higher than the mass dissolved in porewaters, significant Se exposure may result from oxidative shifts in Se associations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018337928312
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  • 8
    Electronic Resource
    Electronic Resource
    Selenium associations in estuarine sediments: Redox effects (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 275-282 
    Details
    ISSN: 1573-2932
    Keywords: selenium ; sediment ; estuaries ; sequential extraction ; redox potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Selenium (Se) is a contaminant of concern in environments affected by discharges from smelting and coal-burning industries. Experiments hate been performed to investigate the phase associations of selenium in contaminated sediments under a range of controlled redox conditions. In this study, Se sediment associations were examined using the BCR sequential extraction technique after stabilisation at different redox states. It was shown that although most of the sediment-bound Se is associated with the operationally-defined “organic sulfide” fraction, as the measured redox potential of the system is increased. more Se moves into the “exchangeable” and “iron manganese oxy hydroxide” fractions. In these fractions. contaminants can be expected to be more bioavailable. As the mass of Se absorbed to sediments is typically at least an order of magnitude higher than the mass dissolved in porewaters. significant Se exposure may result from oxidative shifts in Se associations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406867
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Dynamics of propene metathesis: Physisorption and diffusion in heterogeneous catalysis (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 204-213 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Simultaneous effects of physisorption, diffusion, and reaction were characterized by dynamic experiments for propene metathesis over rhenium oxide/γ-alumina catalyst in a Berty reactor. Single-component sorption isotherms from steady-state experiments for ethene, propene, and 2-butene were used to predict multicomponent physisorption by the ideal adsorbed solution theory. Effective diffusivities were determined from molecular, Knudsen, and surface-diffusion coefficients, including bimodal pore-size effect and tortuosity factors. Transient sorption diffusion experiments were conducted with inactivated catalysts. The reaction rate expression, derived from elementary steps of carbene mechanism, was identified by solving the inverse problem with step test data. The direct problem was solved by orthogonal collocation within the method of lines. Model predictions agreed with responses from dynamic experiments carried out under conditions different from those used for estimating model parameters.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420117
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